The present invention relates to proportioning valve apparatus for mixing first and second gas or fluid inputs to produce a mixed output. Additionally, the present invention relates to control systems for controlling a proportioning valve.
Mixing different liquids or gases to achieve a desired proportion is a time consuming and tedious task. Often this endeavor is undertaken by physically measuring a first gas or liquid and then adding that first liquid or gas to a measured amount of a second gas or liquid. Measurements may be conducted by means of volume or weight. The combined material must then be mixed to achieve a desired consistency. Unfortunately, this is a time-consuming process requiring a plurality of mixing containers and considerable manpower. For example, in the field of liquid compositions utilized to combat forest fires, the compositions often comprise a concentrate and a dilution of water which must be mixed at various proportional rates from 4.5:1 to 10:1 parts per water per part of concentrate. Various apparatus and methods have been employed in an effort to accurately and efficiently produce these fire fighting compositions including the manual measuring and mixing methods described above.
Unfortunately, present proportional valves and the control means for controlling these proportional valves are unsuitable for accurate and efficient production of an effluent mixture. For example, U.S. Pat. No. 4,561,629 discloses a solenoid valve for mixing gases to produce a desired output. Unfortunately, the output is produced by continuously cycling the solenoid valve at up to 20 Hz. Further, this valve is particularly inefficient as the first and second inlets are incapable of both being unobstructed at any one moment.
An additional solenoid valve is disclosed in U.S. Pat. No. 4,428,558. This reference discloses a valve apparatus including a single inlet conduit which directs a gas into a mixing chamber. The gas is then diverted to first and second outlets. Unfortunately, the device is not disclosed as being suitable for both gas and liquid flow. Furthermore, the valve is only configured with a single inlet to separate a single input flow into divergent conduits. In contrast, a proportioning valve is needed for mixing a plurality of gases or fluids to produce a single output mixture.
A control system for controlling the mixing of a first fluid at a first temperature with a second fluid at a second temperature is disclosed in U.S. Pat. No. 3,721,386. The control system includes measuring the temperature of the output fluid to control operation of a valve to proportion the mixture of the first fluid to the second fluid. Unfortunately, the control system is unsuitable for mixing gases or liquids where the inputs are at the same or substantially similar temperatures.
It would be advantageous to have a proportioning valve that accurately and precisely mixes first and second fluid or gaseous inputs into desired proportions to produce a desired fluid or gaseous mixture. Further, it would be advantageous to have a control system for controlling a proportioning valve to accurately and precisely mix first and second fluid or gaseous inputs to produce a desired fluid or gaseous mixture.